In a bid to further the utility of Google Maps, the tech giant is adding live updated mass transit information for New York, Washington, D.C., and Salt Lake City that makes it easier for users to plan their trips.

Riders of the nation's busiest subway system can access the Metropolitan Transportation Authority's data for New York City subway train arrivals at specific stations, as well as information on delays. However, the information is only initially available on the six numbered lines of the IRT system (1-6, excluding the cross-town 7) and the Times Square Shuttle. The range of that system extends from Brooklyn up the East and West Sides of Manhattan to the Bronx.

By the Numbers

It's an upgrade for Google, which previously provided only scheduled, not actual subway departure times. The information is already provided to riders on platform displays.

Departure times are also available for buses and trams in the greater Salt Lake City area and service alerts are available for the Metrorail in Washington, the second-largest system in the country. Using the live alerts for unplanned delays, users can plan an alternate route using Google maps.

"We want to make sure you have access to the most comprehensive, accurate and useful information when you're on the go -- and that includes public transportation," wrote Soufi Esmaeilzadeh, Google Maps' partnership development manager, in a post Wednesday on the LatLong Google Maps blog.

Travelers could already plan trips via mass transit via HopStop.com, which offers directions in dozens of cities and also has recently added tabs for service alerts and schedules, but not live updates for individual stops. Google must also compete with Nokia's Transit App for Windows phones, which provides stop-by-stop directions in 100 cities.

Google is leading the way in cashing in on the smartphone explosion -- shipments of connected devices grew 29.1 percent year over year in 2012, according to IDC Research. Getting more people to use location-based services such as maps allows Google to create personalized ads, one of the most lucrative forms of online revenue today.

Tough to Track

Google has invited any agency that provides transportation with fixed schedules in Africa, Asia, Australia, Europe, North America and South America to be a partner in adding information to Google Maps. Information about schedules and fares is available for 800 cities in 25 countries; live trip updates, however, are only available in select cities

Technology consultant Rob Enderle of the Enderle Group told us the service is not without obstacles in helping Google sell personalized, location-based ads.

"What's a little tough is getting a GPS reading while you're in a subway, making this a bit less useful than it otherwise would be," he said. "But yes, this will likely help [Google] differentiate between people on roads and people in subways so they can better connect them to ads and track their behavior to develop more accurate profiles of them."